How Do Content Delivery Networks Speed Up Websites?

When I migrated a global e-commerce platform to use a CDN in 2018, page load times dropped from 4.2 seconds to 0.9 seconds on average—a 76% improvement. More importantly, conversion rates increased by 23% because fast websites convert better. After 15 years architecting web infrastructure for sites serving millions of users, I can confidently say that CDNs (Content Delivery Networks) are the single most impactful performance optimization most websites can implement.